A horrific day turned to a night of unspeakable grief as parents received formal notifications that their children were killed in the Connecticut school massacre.

The last of the dozens of bodies – most of them children – were removed by early Saturday from Sandy Hook Elementary School in Newtown, Conn., as police narrowed in on a motive and released the names of the victims.

Investigators have found "very good evidence ... as to how, and more importantly, why, this occurred," State Police spokesman Lt. J. Paul Vance told reporters. He didn't disclose what this evidence was.

Earlier, Vance said police had "worked well through the night."

"Our objective certainly was to positively identify the victims to try to give the families some closure," Vance tells CBS News.

The gunman, identified by multiple law enforcement sources as 20-year-old Adam Lanza, killed 20 children and six adults, before taking his own life at the school. His mother also was killed at a different location, bringing the death toll to 28.